Preparation And Characterizations Of Branched And Hydrogenated TiO₂ Nanorod Arrays Electrode With Photocatalytic Performances

Hydrogen energy as a clean new energy,its application prospect is very broad.Under sunlight irradiation,the photolysis splitting water to hydrogen as one source of hydrogen energy has an important significance.Recently,TiO₂ nanorod arrays have attracted wide attention on photocatalysis hydrogen production because of its special structure and activity.But bandgap of TiO₂ is wide and the photocatalytic efficiency is relatively low.Therefore,it is an important research direction to modify TiO₂ to improve its photocatalytic efficiency.This paper focuses on the modification of TiO₂ nanorod arrays,and the main contents and conclusions are as follows.1.The TiO₂ nanorod arrays were prepared by hydrothermal method and hydrogenation treatment,the hydrogenated TiO₂ nanorod arrays?H-TNRs?were obtained and effect of nanorod length on its photocatalysis activity was investigated.The research showed that with the hydrothermal time longer,the nanorod of H-TNRs was arranged more closely,the array was more obvious,the average equivalent diameter and length increased gradually.The crystal phase of H-TNRs was rutile,and nanorod grew toward?001?direction.The photoelectrochemical activity of sample prepared with hydrothermal time of 9 h?H-TNRs-9 h?was the best.The prepared H-TNRs-9 h were used for photoelectric oxidation of organic.The result showed that the net charges generated during photocatalytic reaction had good correlation with chemical oxygen demand?COD?of organic in a range?0-288 mg·L-1?.Based on this,a photoelectrochemical COD?PeCOD?sensor was designed using visible light.The COD obtained by PeCOD is consistent with the standard COD measured by dichromate chemical method.The operation of this sensor was simple,fast and cost-effective.2.The firstly hydrogenated and then branched nanorods arrays?B/H-TNRs?and firstly branched and then hydrogenated nanorods arrays?H-BTNRs?were designed and prepared successfully by adjusting the order of hydrogenation and branching.The structure showed that the branches of B/H-TNRs had none disorder layer,but there was disorder layer about 1.8 nm on the branch of H-BTNRs.There were Ti3+ on two samples,but the content of B/H-TNRs was lower than that of H-BTNRs.The hydrogenation could improve solar light absorbance on both UV and visible light region.The hydrothermal time of branching would affect structure and property of B/H-TNRs,and the photocatalytic activity of 1 h was the best.The photocurrent and photocatalytic hydrogen evolution rate of B/H-TNRs under simulated solar irradiation were 1.6 and 2.4 times of H-BTNRs,respectively.The structure and mechanism analysis showed that the heterojunction between rutile TiO₂ branch and unhydrogenated nanorod promotes separation of photogenerated carrier,improves the photocatalytic activity.3.Anatase-rutile TiO₂ heterojunction branched nanorod arrays?ATNRs?were prepared by hydrothermal method,and structure and photoelectrochemical property of ATNRs were compared with rutile-rutile TiO₂ branched nanorod arrays?BTNRs?.The result showed that ATNRs and BTNRs were both 3-dimensional structure,branches on ATNRs were like thorns about 50 nm,but branches on BTNRs were like needles about 80 nm.The optical absorption of ATNRs and BTNRs were stronger than that of TNRs.The fluorescence of ATNRs was lower than that of BTNRs,that is to say,recombination of photogenerated electron-hole was improved.Both of them had good photoelectric stability under simulated solar irradiation.The photocurrent and photoelectric hydrogen evolution rate by water splitting of ATNRs under 0.23 V were 3.18 mA·cm-2 and 45.78 ?mol·cm-2·h-1,which were both 2 times of BTNRs.The results showed the heterogeneous junction between anatase and rutile increased photoelectrocatalytic activity.The photoelectrochemical analysis showed the fixation resistance of ATNRs was much lower than that of BTNRs,indicating that ATNRs have more efficient photogenerated carrier separation ability,resulting a higher photoelectric conversion efficiency.